As the Boards have often pointed out, when comparative tests are chosen to demonstrate an inventive step, the nature of the comparison with the closest state of the art must be such that the effect is convincingly shown to have its origin in the distinguishing feature of the invention (see e.g. T 197/86).
As we shall see in the present decision, this does not mean that minor differences in the experimental conditions cannot be accepted, especially when the effect obtained is considerable.
The patent proprietor filed an appeal after the Opposition Division had revoked its patent. After having found the claimed subject-matter to be novel, the Board assesses compliance with A 56.
[4.1] The patent in suit is directed to a method for producing an amide involving the preparation of an intermediate mixed anhydride. It is not disputed by the parties that document D3 also relates to such a method, involving the same starting products than the process according to claim 1 in dispute and that document D3 discloses already the combination of Boc-amino protecting groups (named tertiarybutyloxycarbonyl) with the use of N-methylmorpholine as a base […]. Although document D3 describes a specific order of addition of the reactants, namely the addition of the carboxylic acid activating agent, i.e. isobutyl chloroformate, to N-methylmorpholine and an acid, i.e. carbobenzoxyglycyl-L-phenylalanine […], it is further accepted by both parties that document D3, in its general teaching, does not define the order of addition of the reactants […], so that the presently claimed process is encompassed by the teaching of document D3. Therefore, the Board considers, in agreement with both parties, that document D3 represents the closest state of the art and, hence, takes it as the starting point for assessing inventive step.
[4.2] Having regard to this prior art, the [patent proprietor] submitted that the technical problem underlying the patent in suit was to provide a method for producing an amide improving the selectivity for the desired product, and improving thereby the yield of the reaction.
[4.3] The solution to this problem proposed by the patent in suit is the method according to claim 1, which is characterized by the specific order of addition of the reactants, i.e. adding the carboxylic acid and the N-methylmorpholine to a solution of a carboxylic acid activating agent.
[4.4] In order to demonstrate that the technical problem as defined above has effectively been solved by the claimed method the [patent proprietor] relied on the results observed in example 12 and comparative example 2 of the patent specification.
According to example 12 the claimed process involving the required order of addition of reactants, i.e. adding a substrate solution containing the acide and N-methylmorpholine to the carboxylic acid activating agent isobutylcarbonate, achieves a yield of 96,0% of the desired amide. When reverting the order of addition of the reactants in comparative example 2, namely when adding the isobutylcarbonate to the acide and N-methylmorpholine the yield achieved is only 60.7%.
It is thus credible that the claimed process which is characterized by the specific order of addition of the reactants improves the yield of desired product. The Board is thus satisfied that the technical problem as defined above is effectively solved by the claimed process.
The [opponent] contested the fairness of the comparison arguing that during the work-up of the product the acidic treatment was not exactly the same in example 12 and in comparative example 2. In addition, the method used for determining the yield was also different.
However, in both examples the obtained organic layer was treated with the same acid, i.e. hydrochloric acid which differed only in its concentration (1% versus 1.8%). In addition liquid chromatography was used for the determination of yields in both examples, although example 12 was carried out with high performance liquid chromatography whereas comparative example 2 involved silica gel liquid chromatography.
The [opponent] who contested the results observed and had thus the onus of proof of his allegation did not rely on any evidence substantiating that these minor differences have an impact on the yield obtained. In these circumstances, in the present case where a large difference of yield in the desired amide is observed, i.e. 60% according to the comparison versus 96% according to the invention, which represents an increase of about 50% in yield, the improvement shown by the [patent proprietor] is so large that it remains credible irrespective of the above differences (see T 1711/06 [3.5.2]).
This argument of the [opponent] must therefore be rejected.
Notwithstanding this finding, the Board finally found the requests on file to lack inventive step and dismissed the appeal.
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